code: def test_call_raises_error_when_offset_is_invalid(
      self, offset: str
  ) -> None:
      mapper = FileMapper()
  
      pathname = f"foo:{offset}:34"
  
      with pytest.raises(
          ValueError,
          match=rf"^The offset specifier of '{pathname}' must be an integer, but is '{offset}' instead\.$",
      ):
          mapper(pathname)
  
file_path: fairseq2/tests/unit/data/test_file_mapper.py
imports: from pathlib import Path
  from typing import Any, Final, Optional
  import pytest
  from fairseq2.data import FileMapper, FileMapperOutput
label_desc: Use image node_id 8 for calling the TestFileMapper obj's underlying member method code with example usage: obj.test_call_raises_error_when_offset_is_invalid(offset) without return types